As conventional fossil energy sources are depleting and environmental protection issue is given increasing concern, the need for a new efficient green energy source is urgent. Lithium-ion battery, a strongly competitive new energy source, earns exceptional interest. In addition to its wide use in current portable mini-batteries, the development of lithium-ion batteries for use in high-power, high-energy power batteries is even more promising. The lithium-ion battery market is growing beyond expectations. The continuous progress is achieved by the development of new and/or enhanced electrode materials, which has led to considerable improvements in terms of both energy and power densities.
Furthermore, lithium-ion batteries are particularly used in electric vehicles (EV) and hybrid electric vehicles (HEV). Nevertheless, the application of these electrode materials is still limited in EV and HEV due to inherently poor rate capability arising from its low electronic conductivity. Since the diffusion of Li ions in and out of the electrode structure is frequently the rate determining step, this must be improved to allow a fast charge and discharge. With this aim in mind, researchers have put substantial efforts on developing new nanostructured materials, which facilitates the Li ion diffusion due to a reduced length within the active material particles and an increased electrode/electrolyte contact area.
A major class of these materials are phosphate-based cathode materials in the form of LiMPO4 (M=Fe, Co, Ni, Mn) with olivine structure. LiFePO4 (LFP) has become a very promising choice among phosphate-based cathode materials. It is well-suited for powering electric vehicles (EVs), hybrid electric vehicles (HEVs), electric bicycles and power tools, because of its low cost, non-toxicity, and environmental benignity. The reversible electrochemical lithium insertion/extraction reactions take place at around 3.5 V (vs. Li/Li+) with a theoretical capacity of 170 mAhg−1. In addition, LFP also has good cycle stability and excellent thermal stability.
Even with the rapidly changing technology space in this field, there presently remains a need for an efficient cathode active material for lithium ion batteries. Further, there is a need for a high performance active material for lithium ion battery to enhance the rate capability and the capacity of the lithium ion batteries.